Weather based renewables tend to be, by their nature, unpredictable. Your solar panel works most efficiently when there are clear skies and no clouds, while wind power clearly needs wind. Anything based on rain requires a good downpour. This means that, although you can store energy in batteries for later, these renewables are very much dependent on the weather. Some places are best suited to use solar power, for example desert areas near the equator, and others for wind power, for example the coastal areas of Scotland. Many more locations get a varied and interesting mixture of sunshine, wind and rain, without any one of these being consistent.
Any portable energy-generator on a larger scale than the solar cell for a school calculator is going to be problematic. Even solar calculators themselves can be a nuisance, as anybody who’s tried to use one in a dim room can tell you. A solar-powered car, bike, or even a laptop needs the user to stay in brightly lit areas. The same applies to wind power. Wind power on any scale needs regular and strong winds. There is no point positioning a wind farm somewhere that only occasionally receives wind speeds of any note. You will get energy, but not very often and not very predictably.
Rain can also provide electricity, but similar problems apply. Although certain parts of the globe receive rainfall you can set your watch by, it is still not consistent. Despite what the residents of wetter areas might feel, there is nowhere on the planet receiving continuous, heavy rain, all the time. In most places, including North America and Europe, the rainfall isn’t particular predictable either. The solution to the natural inconsistency of the weather would be to harvest two or more renewable energy sources with one generator, and this is exactly what has been done.
Recently, a research team in the UK has combined renewables to form energy-generating ribbons with great potential. The team, from the Institute for Materials Research and Innovation at the University of Bolton near Manchester in the UK, considered the fact that weather, especially in Britain, is highly unpredictable and decided to make a material that used more than one type of weather to produce electricity.
The key to such materials is piezoelectricity, which simply means a charge produced when a solid is subject to pressure or stress. Piezoelectric materials are actually quite common and include familiar substances such as crystals, for example quartz, some ceramics and even the bone and DNA in the human body. Other materials can be made piezoelectric by changing their structure. When something moves such a solid, it creates electricity, which can be collected and used. Raindrops provide light pressure when they fall on a flexible piezoelectric material, as does wind. Humans also provide stress when they physically move the material.
The first step the team made in moving from the theoretical to the practical was finding a convenient material to use wind and rain power. The researchers created 8-inch long ribbons of a piezoelectric polymer, specifically a polyvinylidene fluoride polymer. Piezoelectric polymers create electricity when something moves them even slightly, for example when rain falls on the polymer or wind disturbs it. The polyvinylidene fluoride polymer was found to generate a particularly high voltage relative to area in tests when compared to similar materials.
Although there is certainly no shortage of wind and rain in the Manchester area, the team also wanted their material to use solar energy, for those occasional bright, still days. They coated the ribbons with flexible photovoltaic film, a material already used for advanced solar products. Finally, electrodes were added to collect the solar energy.
Because the raw materials are cheap and flexible and the processing relatively inexpensive, these ribbons could eventually be incorporated into all sorts of items, from clothing to computers. Although small amounts of the ribbon only generate a tiny amount of power – a few milliwatts on average per couple of square inches – large areas would produce significant quantities. The researchers say that the ribbons could easily be folded into “pinecone-like” structures to maximize the surface area packed into a small space, thus collecting more solar energy.
One ongoing issue with solar installations is providing a large enough surface area, which is why most require an extensive area of roof or else a set of dedicated stand-alone panels. Material that can be folded in the manner of the polyvinylidene fluoride polymer has the potential to form larger generators than the researchers are currently considering. Since these folded structures would also move in response to raindrops or wind, they’d keep producing energy even on overcast, stormy days.
The base material for such generators doesn’t have to be the polymer selected by the MRI team. This one was particularly efficient, but there are plenty of other piezoelectric materials. Even your basic nylon can be formed into an electricity-generating polymer. The researchers proved this when they extruded nylon into fibres within a powerful electric field, producing another piezoelectric material.
By adding photovoltaic film to the piezoelectric nylon, the material uses the sun in addition to converting the wind and rain into electricity. The possibility of creating clothing that generates electricity in all weathers, something that hikers and other outdoor enthusiasts might find extremely useful for powering phones, cameras and perhaps even heaters, is not far away. Along with the energy collected from wind, rain and sun, electricity would also be generated simply by the movement of the wearer.
Adding a battery to such clothing would mean you could take the dog for a nice walk and use the electricity generated in your home later. Battery technology is developing as quickly as renewable energy technology, with batteries becoming smaller, lighter and a lot greener. Combining the technologies would mean futuristic products that are more than cute novelties; they would help to combat the many and varied problems associated with the use of fossil fuels.
George lives in Grants Pass Oregon and works for ImpactBattery.com. An avid outdoorsman and environmentalist, he writes about topics related to all kinds of recreational vehicles and accessories. He is also the “go to guy” for information when shopping for items like portable solar chargers and marine battery chargers.